Crude clay materials, particularly kaolin clays, as mined, contain various forms of discoloring elements, two major impurities being titaniferous compounds, usually in the form of anatase (TiO.sub.2) and iron oxides. In order to improve the physical properties of these clays and make these clays more acceptable for use in the paper industry, the impurities must be substantially removed by appropriate techniques.
The production of high brightness clays requires removal of discoloring impurities from the clays. Removal of impurities usually includes two processing steps. In the first step, a significant portion of the impurities, mainly anatase is removed by employing one or more physical separation techniques, such as high gradient magnetic separation (HGMS), froth flotation and selective flocculation. In the second step the remaining impurities, mainly iron oxides, are removed by chemical leaching.
Of the known physical separation techniques, one of the most efficient commercially-practiced beneficiation techniques for improving the brightness and appearance of sedimentary clays, particularly kaolin clays, is removal of iron-stained antase particles by froth flotation.
Froth flotation processes for removal of anatase from kaolins involve the addition of a class of chemical reagents, commonly called "collectors". These collector reagents are surfactants, i.e., molecular entities of a Janus character with one end of the molecule having a polar functional group and the other end, a non-polar functionality. Incorporation of suitable collector reagents into kaolin slurries along with concurrent regulation of the activities of accessory chemical species present in the aqueous phase of the slurry, will result in the selective adsorption of the polar portion of the collector molecule onto the surface of an anatase particle. Upon adsorption, the non-polar portion of the adsorbed collector species will be exposed to the aqueous portion of the slurry and cause the anatase particles to have a hydrophobic character. In this state, the anatase particles can attach to a rising stream of air bubbles, as generated in a froth flotation cell, and thereby be removed from the kaolin slurry.
The more commonly used collector reagents for flotation of anatase from kaolin slurries are aliphatic fatty acids such as oleic acid (cis-9-Octadecenoic acid). An example of a flotation process employing oleic acid for flotation of anatase from kaolin slurries may be found in U.S. Pat. No. 3,450,257 to E.K. Cundy.
The present invention provides a method for improved froth flotation removal of contaminates by use of a novel flotation aid that works in conjunction with conventional collection reagents to produce mineral products, such as clays, which have significantly less contaminates than those processed by conventional flotation processes.